Gelatinous sea creatures shut down nuclear plant

California was without nuclear power on Thursday after a swarm of jellyfish-like creatures forced the shutdown of the Diablo Canyon plant in San Luis Obispo County.

Plant operator Pacific Gas & Electric took its Unit 2 reactor offline in the morning in response to a dayslong invasion of salp -- a translucent plankton-eating organism that can rapidly reproduce. Intake pipes for sea water become clogged with the creatures, threatening the plant's cooling system.

"They became so voluminous that we decided to do what is in the best interest of the plant and safety ... and shut it down," PG&E spokesman Tom Cuddy said.

The decision leaves California, at least briefly, without nuclear power generation, which ordinarily accounts for about 14 percent of the state's electricity mix.

The second reactor at the Diablo Canyon plant in Avila Beach was taken offline earlier this week for routine fueling and maintenance.

The San Onofre nuclear plant between the cities of Los Angeles and San Diego has been offline since January as operator Southern California Edison tries to resolve the unusual, rapid degradation of tubes inside recently replaced steam generators.

Some marine creatures are easily sucked into power plant intake pipes -- one reason California is phasing out or refitting once-through cooling plants by law over the next decade.

In 2005, a school of anchovies swam too close to the San Onofre Nuclear Generation Station, leaving plant workers to clear 11,000 pounds of dead fish from intake filters. In 2004, 14,000 pounds of sardines met the same fate.

At full capacity, the Diablo Canyon provides about 2,300 megawatts of power, slightly more than San Onofre. Together, the plants can power roughly 3 million homes.

Power reserves were plentiful on Thursday amid mild weather, according to the state's main electrical grid manager, the California Independent Service Operator.

Cuddy, of PG&E, said Diablo Canyon would remain offline until the salp migrate elsewhere.